The present invention relates to imaging optics, particularly to optics on the distal end of a flexible fiberoptic endoscope or rigid borescope inspection tool, and more particularly to an optic having a narrow (<20 degrees) field of view with very low optical distortion (<5% pin cushion or barrel distortion), while at the same time having a prescribed chromatic focal shift.
Current inspection methods depend upon either the visual judgement of a human operator and/or the costly and time consuming disassembly of complex or hazardous hardware. In industrial or laboratory settings, it can be either not cost effective or too hazardous to perform such work. In addition, the operators subjective visual judgement as to the condition of a component can depend upon factors such as lighting, visual fatigue or time available to make the determination. Also, the measurement of the surface roughness in the turbine blades of an electrical power generator, for example, can put a unit out of service for a significant time and reduce efficiency of the station and cause cost to increase to the end user as well.
For the inspection and measurement of surface roughness on the interior of mechanical constructions, it is not always possible to use optical interfero-metric or mechanical measurement techniques. Close, cramped spaces and the inability of disassembly forces this measurement to be made by other means. Typical surface metrology involves a stylus profilometer being drug across a surface for contact measurements. For non-contact measurements, white light phase shifting optical interfero-metric methods are used when the part can be transported to the interferometer. When such disassembly and transport are not possible or practical such as in-siter nuclear reactor fuel rod inspections, nuclear weapons pit inspections, medical settings, etc., other methods must be developed and employed.
The optics of this invention will allow data to be taken optically and post processed to gage material condition. The subsequent computer processing of this data can give a go/no go reading on surface topology and aid in the decision processes for further action. The optics of this invention is optimized for high spatial resolution, minimal nonlinear magnification distortion while at the same time having a prescribed chromatic focal shift. The image coverage is over a narrow (<20 degrees) field of view with very low optical distortion (<5% pin cushion or barrel distortion).